Continuously molded thermoplastic materials

ABSTRACT

A THREE-DIMENSIONAL FUSED MOLDED PRODUCT MADE FROM THERMOPLASTIC MATERIALS IN A CONTINUOUS INJECTION MOLDING PROCESS. THE PRODUCT COMPRISES A PLURALITY OF SPACED APART CUPS WHICH DEFINE DRAINAGE AREAS BETWEEN ADJACENT BASE STRIPS TO WHICH THE CUPS ARE CONNECTED. THE CUPS HAVE CUP WALLS EXTENDING OUTWARDLY FROM A COMMON PLATE SURFACE AND ARE EQUIPPED WITH PLURALITY OF ELONGATED CUP PROJECTIONS WHICH ARE INTEGRAL WITH AND EXTEND OUTWARDLY FROM THE CUP WALLS.

24, LE ET AL CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS Original FiledSept. 12, 1969 8 Sheets-Sheet 1 WILLIAM H. HILLS JACK DOLEMAN ORNEYApril 24, 1973 J. DO-LEMAN ETAL 3,729,364

CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS Original Filed Sept. 12,1969 8 Sheets-Sheet 2 m wj; Q L 1 N6 i 1 FIG. 2.

4 I H\ /ENTOR9 WILLIAM H. HILLS TORNEY April 1973 J. DOLEMAN ETA!-CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS 8 Sheets-Sheet OriginalFiled Sept. 12, 1969 FIG. 4. F/G.5.

FIG]

FIG. 6.

FIG.9.

FIG. 8.

INVENTORS WILLIAM H. HILLS JACK DOLE/A71 TORNEY A ril 24, 1973 3,729,364

J.DOLEMAN ETAL CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS OriginalFiled Sept. 12, 1969 8 Sheets-Sheet INVENTORS WILLIAM H. HILLS JACKDOLEMAN ATTORNEY A ril 24, 1973 J. DOLEMAN -ETAL CONTINUOUSLY MOLDEDTHERMOPLASTIC MATERIALS 8 Sheets-Sheet 5 Original Filed Sept. 12, 1969FIG. /2

INVENTORS WILLIAM H. HILLS JACK DO April 24, 1973 J. DOLEMAN ET ALCONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS 8 Sheets-Sheet 6 OriginalFiled Sept. 12, 1969 FIG. /5.

FIG. 16.

INVENTORS WILLIAM H. HILLS JACK DOLE/77X] ORNEY April 24, 1973 DOLEMANETAL 3,729,364

CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS Original Filed Sept. 12,1969 8 Sheets-Sheet 7 INVENTORS WILLIAM H. HILLS TORN E Y April 24, 1973DOLEMAN ET 3,729,364

CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS Original Filed Sept. 12,1969 8 Sheets-Sheet 8 FIG. 22.

INVENTO S WILLIAM H. HILLS JACK DOLEMAN Mxf United States Patent3,729,364 CONTINUOUSLY MOLDED THERMOPLASTIC MATERIALS Jack Doleman, GulfBreeze, Fla., and William H. Hills, Durham, N.C., assignors to MonsantoCompany, St. Louis, Mo.

Continuation of application Ser. No. 857,461, Sept. 12,

1969, now abandoned, which is a division of application Ser. No.650,986, July 3, 1967, now Patent No. 3,507,010. This application July1, 1971, Ser. No.

Int. Cl. B32b 3/10, 3/12 US. Cl. 161-36 1 Claim ABSTRACT OF THEDISCLOSURE This application is a continuation of Ser. No. 857,461, filedSept. 12, 1969, and now abandoned, which is a division of Ser. No.650,986, filed July 3, 1967, and now Pat. No. 3,507,010.

BACKGROUND OF THE INVENTION The continuous production of molded articlesin essentially flat sheet is well known in the prior art. Examples ofsuch articles include flat mats, webs, nets and the like, which aregenerally regarded as being two-dimensional since the ratio of thicknessto width is very small. The production of these essentiallytwo-dimensional articles can be accomplished in a continuous operationby apparatus such as that disclosed in French Pat. No. 1,246,923. Inthese molding processes however, the shaping of the plastic materialoccurs between opposed rolls which are generaly patterned or engravedonly slightly to impart not more than a slight three-dimensional effect.While these processes appear to be suitable for molding thintwo-dimensional products, it is quite obvious that they could not beemployed for the production of thicker structures having longprojections on one side of the matrix since leakage of the moltenmaterial would occur from the high pressure required to make suchproducts. Thus, the major drawback encountered with the methods taughtby the prior art is the inability to produce products having heavysectioned members in the backing and thin section members extending fromthe backing.

Heretofore, truly three-dimensional molded products have been producedonly by the batch method on a conventional injection molding machinewhich is time consuming and thus expensive. By truly three-dimensionalmolded products is meant products having portions such as projectionsthat are substantially greater in dimension than the structure whichinterconnects and supports said portions. Conventional injection moldinginvolves a sequence of steps that must be carried out separately. Thesesteps include heating the mold after closing and injecting the moltenmaterial into the hot mold to permit the void areas fo become filled.The mold is then chilled to solidify the molten material beforeseparating the mold parts and removing the molded article. Therefore, itis readily apparent that a majority of the time required to carry outthe batch-type method is contributed to essentials other than molding.

3,729,364 Patented Apr. 24, 1973 ICC SUMMARY OF THE INVENTION Inaccordance with the present invention a molten thermoplastic material isfed from a suitable source to an extrusion nozzle by a conventionalmetering pump or screw extruder. The material is forced into recessedareas in advancing associated molds under varying pressures dependingupon the size and depth of the mold cavities. The material is cooledbelow its solidification point and stripped away from the mold incontinuous lengths.

The continuous injection molding process of this invention is carriedout by feeding a molten thermoplastic material to an extrusion nozzlepositioned against an advancing mold surface having a multiplicity ofcavities therein which are interconnected by grooves either in theadvancing surface or the surface of the adjacent extrusion nozzle,applying sufficient hydraulic pressure upon the molten material to forcesaid material into the cavities and grooves, causing the material toflow downstream in the grooves in the direction of travel of theadvancing mold surface to form a network of strips which interconnectthe cavities, cooling the shaped structure until slidification occurs,and then stripping the structure from the advancing surface. Ifpreferred, the shaped structure may be compressed between opposedmembers before take-up.

The basic principle involved in the production of the products of thepresent invention encompass the application of two zones of pressureswithin the molding equipment for the molten material wherein a highpressure zone is isolated for the purpose of forming the thin sectionsor projections and a low pressure zone for forming the heavy sections ormatrixes of the three-dimensional product. By employing separatepressure zones sufficient pressure can be applied to fill deep cavitieshaving small cross-sections while simultaneously controlling thepressure in the low pressure zone to prevent leakage from the largegrooves to the outside which would disrupt the operation.

Obviously several different arrangements of apparatus may be employed inthe practice of this invention and particularly the means that can beused to separate the high pressure zone from the low pressure zone. Forexample, pressure fingers attached to the stationary extruder block ormade integral therein may be dimensioned to occupy the space oflongitudinally extending grooves in the advancing mold surface. Thesefinger members serve to isolate the cavities to facilitate achievementof a high pressure therein and to prevent back flow of the moltenmaterial in the circumferential grooves where a lower pressure exits.Preferably the molten material is fed to the two pressure zones inseparate streams with the high pressure extrusion ports .being locatedwell upstream of the downstream end of the pressure fingers and the lowpressure extrusion ports being located over the circumferential groovesdownstream from said end of these fingers. As a matter of conveniencemolten material to both the high pressure and low pressure extrusionports may be supplied from a common source provided metering valves arelocated in the low pressure supply lines between the extruder and thelow pressure extrusion ports wherein a desired pressure drop ismaintained to control the amount of molten material being introducedinto the grooves where the heavy section part of the product is formed.If desired the high pressure and low pressure ports may be supplied fromseparately metered sources by conventional pumps capable of controllingthe pressures at their respective proper level.

In an alternative apparatus for introducing the molten material to themolds, a single row of extrusion ports are aligned for communicationwith the moving mold cavities initially to exert a high pressure asrequired to fill the recessed areas of the deep cavities. Uponadvancement of 3 the mold-containing cavities communication between thecavity areas and the circumferential grooves is established for aninterval suflicient to fill the grooves with the molten material. Duringthis part of the cycle the relative position of the forward end of thepressure fingers and wall of each cavity become gapped enough to metermaterial into the grooves under lower pressures which fill the groovesand connects the cavities together to produce a continuous producthaving perforations suitable for drainage. Since any wear of thepressure fingers will alter the metering characteristics of the materialflowing to the grooves, this type of feeding system is not as preferableas the dual set of extrusion ports.

The above described principles are applicable to various embodiments ofequipment which include a rotatable drum on a series of laterally movingplates in conjunction with a stationary extrusion member having a facearea in contact therewith. This equipment may be further modified bytransferring the longitudinally extending grooves from the surface ofthe drum or plate to the face of the extrusion member, in whichinstance, a product having a continuous stringer or heavy sectionedmember would be formed to produce a ribbed back. Similarly, a solidbacked product can be produced by employing a single groove the Width ofthe product instead of a plurality of grooves. Also, contemplated is theuse of opposed cylindrical drum surfaces wherein one surface containscavities and the other surface has circumferential grooves, the cavitiesbeing filled from a source under a high pressure and the grooves filledfrom a lowerpressure source.

In carrying out the invention by utilizing a series of flat plates inplace of a drum or opposed drums, extra equipment is required in orderto convey the plates into and out of position with the stationaryextrusion member. Conveying means are required to take the flat moldsafter the product is cooled and stripped on the downstream side of thepolymer block, and recycle them back around to the upstream side of theblock for remolding. When the plates fit properly against each other,molded product is produced in indefinite lengths by this method. Forsome applications, such an arrangement might be desirable. As an exampleif one desired to produce the mold segments by some low-cost processsuch as die casting where it would be desirable to make each element ofthe mold as small as possible, thereby using a number of these elementsto form a large enough working mold to facilitate carrying out theprocess. Another possible advantage might arise if someone desired tovary the shape of the mold product along its length in a non-repeatingpattern. This could be accomplished by having mold segments of differentconfigurations and sorting these mold segments according to somepredetermined pattern as they were conveyed from the downstream side ofthe polymer block, back around to the upstream side.

All moldable thermoplastic materials may be employed with the presentinvention. Highly preferred materials are polyolefins such aspolyethylene and polypropylene; polyvinyl halides such as polyvinylchloride, polyvinylidene chloride, polyvinyltetrafluoride, polyvinylchlorotrifluoride; polyvinylesters such as polyvinyl acetate; andmixtures or copolymers thereof. Other preferred materials includethermoplastic condensation polymers such as polyamides, segmentedpolyurethanes, polyurethane rubbers, silicon rubbers, natural andsynthetic rubbers and polyesters. In some cases the properties of theproduct may be modified to improve its appearance or durability andperformance through the addition of various pigments and stabilizers.

The thermoplastic material may be supplied to the extrusion nozzle byany conventional means capable of maintaining the material in a moltenstate and conveying the same under suflicient pressure to the moldsurface. The mold surfaces, which will be described later herein, may bedriven by any conventional means capable of synchronizing the speedthereof with the linear output of the thermoplastic material.

The molded objects are cooled to about 50 C. below the thermoplasticstate of the material from which it is made and stripped away from themold surface with the aid of a set of stripping fingers positioned inalignment and engaged within the longitudinal grooves. Cooling of theproduct is accomplished by spraying a coolant such as air or waterdirectly onto the product itself, or mold may be cooled by a surfacecoolant or passing a coolant through the inside of the drum, whereapplicable.

For some end products a texturing step may be desired to modify theaesthetic properties such as causing the vertically extending members toassume the random haphazardness shape of natural grass blades. Thetexturing step may be carried out as an in-line step upon removal of theproduct from the drum, or at a later time. Preferably, the texturing isaccomplished by a pair of opposed rolls, converging belts, or areciprocating plate in conjunction with a fixed member while the productis heated to a temperature at which the material may be permanentlyheat-set.

The principal advantage realized from this invention is the fact thatindefinite lengths of the product can be made in wide widths therebyreducing the production and installation costs drastically. While thewidth may vary considerably it has been found that widths of at least 4inches are preferred because of the economics involved. Also, theproduct should be in great lengths. Accordingly, the productcontemplated by the present invention has a length at least 10 timesgreater than the minimum 4 inch width. Unless this minimium ratio isobserved the advantages afforded by this invention cannot be realizedsince the economic gains will be diminished. Furthermore, forinstallations such as ski slopes where joints or seams may be hazardous,it is highly preferable to have the surface made from wide continuouslengths which run parallel down the slope.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofthe preferred embodiment of apparatus for carrying out the process ofthis invention;

FIG. 2 is a cross-sectional view, in part, of the drum and extruder headof FIG. 1 illustrating, in detail, the construction of the drum andassociated equipment;

FIG. 3 is a fragmentary perspective view of the drum surface andextruder head illustrating the path of comrnunication between saidmembers and the three-dimensional profile of the drum surface;

FIGS. 4-7 illustrate, in sequence, the relative positions of the drumand the extruder head through a partial revolution of the drum tofurther illustrate the injection cycle employed to produce the productof the present invention;

FIG. 8 is a pictorial view of the product as it is stripped from thedrum and further illustrates the perforations in the base of the productin addition to the cups formed at the base of the projecting members;

FIG. 9 is a pictorial view of the product shown in FIG. 8 after havingundergone a texturing treatment which imparts a grass-like resemblenceto the product;

FIG. 10 represents an alternative embodiment of apparatus, shown incross-section, which may be employed to practice this invention wherebya number of flat-plate dies are employed rather than a cylindrical drum;

FIG. 11 is a perspective view of the die plate used in the arrangementshown in FIG. 10 which illustrates the details of the mold surface;

FIG. 12 is a cross-section of opposed rotatable drums wherein one drumsurface is provided with rows of cavities interconnected by grooves andthe other drum surface is provided with parallel grooves circumscribingthe cylindrical surface thereof;

FIG. 13 is a fragmentary view of the drum in FIG. 12 having theinterconnected cavities illustrating the surface design;

FIG. 14 is a fragmentary view of the other drum in FIG. 12 which hasparallel grooves around the surface thereof illustrating the polymersupply and extruder fingers;

FIG. 15 is a cross-sectional view, in part, of the drum and extruderhead of FIG. 1 wherein the extruder head is provided with separateorifices for introducing the low pressure and high pressure materialsupply separately;

FIG. 16 is a fragmentary view of the drum surface in FIG. 15illustrating how the cavities and the parallel grooves are supplied bypolymer from individual sources;

FIG. 17 relates to the operation of the embodiment shown in FIG. 16 andillustrates the polymer injection positions in conjunction with theformation of the product;

FIG. 18 represents fragments of a drum and extruder head with portionsof each broken away to illustrate the extrusion grooves in the face ofthe extruder head and the high low pressure supply orifices;

FIG. 19 relates to the operation of the embodiment shown in FIG. 18 andillustrates the polymer injection positions in a plan view inconjunction with the formation of the product produced thereby; and

FIG. 20 is a cross-sectional view of the product produced on anembodiment as shown in FIG. 18 illustrating the ribbed back which isformed in the grooves in the face of the extruder head.

FIG. 21 is a fragmentary portion of a drum illustrating wedge-shapedgrooves extending across the drum in place of the rows of cavities.

FIG. 22 represents the product made from the type embodiment shown inFIG. 21.

With reference to FIG. 1, there is shown the general arrangement ofapparatus preferred for practicing the invention wherein an extruder 10of a well known type is provided with an extruder head 12 which ispositioned in contact with a drum 14. The extruder is provided with fans16 and resistance heaters, not shown, which are powered from anelectrical source for controlling the temperature of the extruder barrelat a desired level. The extruder head 12 has a concave outer edge whichfits flush against the surface of drum 14. This close contact ismaintained through the linkage arms 18 and 20 which are pivoted by apneumatically operated cylinder 22 to move the drum 14 into and out ofcontact with the extruder head 12. A motor 24 rotates the drum 12 at aselectively predetermined speed in the direction indicated by the arrowto advance a molten thermopalstic material deposited on the drum at theextruder head 12. A cooling medium is introduced into the drum at theinlet 26 and collected in a drip pan 28 having a drain outlet 30. Thesolidified material is stripped from the drum by a multipronged device31 referred to herein as stripping fingers and is then taken up in aroll as shown. As an optional step in the process, the product 33 may betextured or heat-set between a pair of pressure rolls 35.

To obtain a better understanding of the more important aspects of thisinvention, reference is made to FIGS. 2 and 3 wherein the details of thedrum surface and extrusion head are more clearly illustrated. In FIG. 2.the the close fitting relationship of the extruder head 12 and drum 14is shown in cross-section to illustrate the extrusion nozzle 32 in acommunicating position with the cavity 34. The cylindrical drum isprovided with a multitude of equally spaced rows of cavities 34 havinginserts 36 press-fitted into these cavities to selectively limit thepenetration of the polymer melt into the drum and thus control theheight of the projections formed from the polymer. Preferably, theinserts 36 are engraved around their circumferences to providelongitudinal recesses 38 (note FIG. 3) which produce relatively thinprojections resembling grass blades. It is to be understood however 6that the inserts 36 are shown merely to illustrate a preferredembodiment of this invention since obviously the inserts may be ofdifferent shapes or they may be removed from the cavities.

Referring to FIG. 3 the polymer supply is injected by hydraulic pressurethrough extruder nozzle 32 into the aligned drum cavity. In order toinject the polymer melt into the extreme depths of the longitudinalrecesses 38 in the surface of the inserts 36, a seal must be maintainedaround the immediate area of the point of injection. This accomplishedby providing the drum surface with the raised portions 40' thateffectively block the flow of the polymer supply in sequence as the drumrotates whereby perforations occur in the final product, and the use ofL- shaped members 42 which fit loosely in the grooves 44 thatcircumscribe the cylindrical drum 14. These L-shaped members function asextruder fingers to prevent the polymer melt from flowing along thegrooves so as to cause a reduction in the pressure essential [forcompletely filling the cavities 3-4. The extruder fingers 42 areinserted in the grooves 44 and retained therein by a plate 46. Withoutthe use of extruder fingers, or their equivalents, the polymer melt hasa tendency to back flow in groove 44 to the extent that the recessedareas 38 around the inserts are not completely filled whereby aninferior product is molded. The polymer is admitted to the grooves 44just before the communication from the extruder nozzle is sealed off bythe raised portions 40 whereupon the polymer flows along said groovesonly in the direction of drum rotation since the pressure fingers blockany flow in the other direction. Thus, it will be recognized that withthe above described arrangement it is possible to separate the supplypolymer into two pressure zones in order to impose the substantialamount of pressure that is required to force a viscous thermoplasticmaterial into confined areas having substantial depths such as about /2inch or greater. It has not been possible to achieve this accomplishmentheretofore on conventional molding equipment.

FIGS. 4 through 7 illustrate the formation of the product in a series ofsteps which show the relationship of the extrusion nozzle or orifices 32and the surface of the drum 14 after the drum has been rotated anincrement in each figure until the drum has progressed through a feedingcycle. Referring to the figures in order, the polymer supply 32 is shownaligned against raised portions 40 in a non-feeding position. As thedrum rotates to the position shown in FIG. 5, the extrusion orificebegins communicating with cavity 34. In FIG. 6 the extrusion orifice isin direct alignment with the cavity at which position the radial flow ofthe material is blocked in all directions by the raised portions 40 andthe extruder fingers 42. Therefore, the polymer melt is forced into thedepths of the cavity to completely fill all recessed areas. Furtherrotation of the drum provided communication with grooves 44 between theend of extruder fingers 42 and the raised portions 40 to supply enoughmaterial to form the stringers 50 which connect the clusters ofprojections to produce a lattice-type construction.

One possible product of this invention is shown in FIGS. 8 and 9. Theproduct in FIG. 8 is depicted in the shape it is stripped away from thedrum and FIG. 9 represents the same product after it has been subjectedto a texturing treatment which flattens the projections 60 to resemblegrass blades. A cross-section of the cup-like to form a linear pathwhile in contact with the extruder head 72. The plates are advancedthrough the feeding cycle and returned to the starting position alongthe path indicated by the line of arrows by a conventional conveyorsystem, now shown. The principles involved in the production of thethree-dimensional products disclosed herein are the same as thosediscussed in connection with the cylindrical drum. For example, as shownin FIG. 11, the plate 70 is provided with cavities 74 which areseparated by protruding plate portions 76. The plate is also providedwith parallel grooves 78 to accommodate the extruded fingers 80 for thesame purpose as earlier explained. The extruder fingers are securedagainst a shoulder forming a part of a cut away portion of the extruderhead. With the extruder fingers and polymer supply being stationarythere is commnication between the polymer supply and the grooves duringpart of the injection cycle after the cavities have been filled, as wasillustrated in FIGS. 4 through 7. The communication occurs between theend of the extruder fingers 80 and an adjacent plate portion 76.

Referring to FIG. and the details illustrated, there is shown a portionof the extruder 10 having the modified extruder head 72 mounted theretoand the plates 70 which are positioned for advancement with their moldsurfaces in contact with the face of the extruder head. The cavities 74are provided with press-fitted inserts 75 which block the flow ofpolymer through the plate 70. The end of the inserts exposed to theextrusion nozzle 32 have grooves spaced around their circumferences topro vide elongated recesses for receiving the polymer melt when thecavity passes in alignment with the extrusion nozzle 32. The plate 70 isadvanced along its lineal path until the molten polymer becomessolidified and then the plate is removed leaving the molded product 77which may be advanced through a texturing step prior to take up or maybe advanced directly to a take-up roll. The removed plate is returned toa starting position along the path indicated by arrows by theconventional conveyor, not shown, where it abuts another plate alreadyadvancing along a lineal path toward the extrusion nozzle therebyproviding a continuous lineal molding surface.

Another embodiment of apparatus useful for practicing the invention isshown in FIGS. 12 through wherein opposed drums are employed to make themolded product described herein. Referring initially to FIG. 12, thereis shown a cylindrical drum 90 having cavities 92 selectively spacedaround the peripheral surface thereof. As illustrated in FIG. 13, whichdepicts a portion of the surface of drum 90, the cavities are connectedwith interconnecting grooves 94. An opposed drum 96 rotates in contactwith drum 90. A fragment of the surface of drum 96 is shown in FIG. 14which illustrates a number of parallel grooves 98 circumscribing thedrum. A11 extruder head 100 having a polymer source 102 is modified toaccommodate partial circumferences of drums 90 and 96 whereby theextruder head is in contact with each of the drums. The polymer supplyis divided into a polymer stream A which is injected into the cavities92 and a polymer stream B which is discharged into the parallel grooves98 forward of the extruder fingers 106 as shown in FIG. 14. A meteringvalve 104 is provided to control the pressure of polymer stream B at alower level than stream A. The finished product 108 is solidified andremoved from drum 90 in accordance with previously stated procedures.

It will be noted that in the apparatus described hereinbefore, theextrusion orifices are positioned axially across the extruder head in asingle row to communicate directly with the mold cavities upon movementof the mold surface. As illustrated in FIGS. 4 through 7, the stringergrooves are filled by polymer flowing from the high pressure Zone intothe grooves through a gap between the pressure fingers and a raisedportion on the mold surface that separate long enough to supply a lowpressure flow of material. The gap functions as a metering valve toreduce the pressure and prevent overfilling. A preferred modification tothis type of feeding system is shown in FIG. 15 which illustrates themolten material from passageway C in direct communication with the drumcavity 110. Similarly, the stringer grooves 112 (note FIG. 16) aresupplied with molten material flowing through passageway D which isprovided with an adjustable metering valve 114. The dual set of moltenmaterial supply sources is more clearly illustrated in FIG. 16. Thistype of feeding system makes it possible to supply a molten polymer froma common source to the mold cavities under pressures high enough tofacilitate injection of the polymer into deep, small recesses and to thegrooves under substantially lower pressures. Thus, in order toaccurately control the system in a particular situation, the pressure ofthe common supply source is controlled to accomplish the injection intothe cavities and the metering valve is adjustable for controlling thepressure as necessary in the low pressure zone. Further illustration ofthis type of dual pressure zone system is shown in FIG. 17, includingthe formation of the product 116.

FIG. 18 represents another embodiment of apparatus that may be employedto carry forth the present invention. In this embodiment, the groovesare cut in the face of the stationary extruder head 122 instead of themold surface. Again the double row of orifices is shown to illustratehow the molten material is supplied to the mold area between extruderhead 122 and the rotatable drum 124 which is shown as a broken-awayfragment to better illustrate the position of the orifices. Material Eis injected into the recesses 125 engraved around the circumference ofpin 126 to form a cluster 128 of thin projections connected in a circleto a cup-like portion 130 which is formed around the dome of pin 126.The clusters are integrally connected to the stringers or heavysectioned portions 132 which are formed in the grooves 120. Thesedetails of the process and product are clearly illustrated in FIGS. 19and 20. Obviously, the depth and width of the grooves may be varied tochange the shape and size of the stringers 132 as desired even to theextent of using a single depth cut away which would produce a producthaving a solid back. In all of these instances the pressure to thegrooves can be controlled by the adjustable metering screws 134.

A further embodiment of the invention is illustrated in FIG. 21 whereina fragment of a drum surface as employed in the previous embodiments isshown to illustrate a different surface design which facilitates theproduction of the product shown in FIG. 22. Referring to FIG. 21 it willbe noted that the surface of the drum is provided with wedge-shapedgrooves extending across the width of the drum which are interconnectedby parallel grooves 142 around the circumference of the drum. As in FIG.16, a dual two-stage pressure feed system is employed to convey moltenmaterial to the deep grooves 140 at a higher pressure and to grooves 142at a lower controlled pressure in accordance with procedures describedearlier herein. The pressure fingers 146 function to isolate the flowbetween the channels so that the material will reach the extreme depthof the groove.

With reference to FIG. 22 which represents the product obtained from thedrum design of FIG. 21, it will be noticed that the wedge-shaped groovesform thin, inverted wedge-shaped projections 148 that are connectedtogether by the widely spaced apart stringers 150 which are formed inthe parallel grooves 142. The stringers 150 have extremely smallthicknesses when compared to the height of the sharp-edge projections148. A product of this type can be employed on newly excavated banks andthe like to prevent soil erosion. The projections will counter thetendency of the soil to wash until grass will grow through the openback.

9 PREFERRED EMBODIMENTS The following examples are given to show thePreferred products and process conditions of applicants invention whichare merely illustrative of the wide variety of products that may beobtained when following the teachings of the invention set forth.

Example 1 This sample illustrates a preferred method of producing acontinuous pigmented polyolefin structure which after compacting issuitable for use as an artificial turf.

Apparatus used was in accordance with that illustrated in FIGS. 1, 15and 16 as previously described.

Polyethylene pellets were melted and fed under hydraulic pressure from 4/2" screw extruder into the special distributing nozzle previouslydescribed. Two rows of holes in the nozzle directed polymer into thecavities and grooves of a mold drum. The first row of holes to contactthe empty mold drum supplied polymer to the deep tuft cavities, thesecond row of holes supplied polymer to the stringer-grooves. Stationaryfingers lying in the grooves of the mold drum isolated each tuft cavitywhile molding took place, thus creating a zone of high pressure whichallowed full depth penetration of the narrow sectioned deep cavities.The aforementioned fingers terminated just upstream of the row of holessupplying polymer to the stringer-grooves. Polymer was deposited in thestringergrooves at a pressure slightly above atmospheric regulated byflow restrictors to control the amount of polymer fed to each groove. Byadjusting the restrictors it was possible to obtain a balance of moldingpressures to completely fill the tuft cavities and product stringersflush with the surface of the mold drum. Sufficient cooling water wasfed to the inside of the drum and allowed to escape down the tuftcavities to maintain the chilling capacity of the drum.

Using a blend of 100 parts polyethylene (Monsanto MPE 87) Melt Index 22and 4 parts green pigmented polyethylene (90% PE, Pigment, a continuousrun of over 2 hours duration was made during which the following processconditions were observed and maintained. Melt temperature measured atextruder exit, 425 F.; temperature of nozzle, 350 F.; temperature ofmold drum surface, 125 F.; pressure at end of extruder barrel, 1350p.s.i.; molding pressure (Tufts), 1100 p.s.i.; molding pressure(stringers), 50 p.s.i., total force holding mold drum in contact withnozzle, 9000 lbs.; peripheral speed of drum, 4 f.p.m.; cooling timebefore stripping product from drum, 30 seconds; cooling water to drum at70 F., 2% gals/min.

The shape of the finished product can best be described with referenceto the shape and configuration of the mold drum. The steel drum used hadan outside diameter of sixteen inches with a wall thickness of 1%" andwas fabricated to produce a continuous product of 6" overall width inthe following manner: 16 circumferential grooves W wide by ,5 deepspaced at .400" centers were turned into the outside face of the drum toform continuous stringers. Equally spaced between the grooves at 3intervals axial rows of fifteen diameter holes were drilled through thewall of the drum. These holes intersected the grooves thus ensuringlateral continuity to the product. Press fitted into each hole was abrass tuft insert 2" long of substantially cylindrical form with eightequally spaced flutes cut on the outside diameter with a radius cutterto a maximum depth of .040", tapering away from the axis of the insert,at 1 4 to a length of 1" from the end nearest the surface of the molddrum. To assist flow of the polymer down the length of the tflutes, theouter end of the insert was made hemispherical and set A below the outersurface of the mold drum. The finished product completely filled themold to produce a product as shown in FIG. 8 having 1 inch tufts onprojections. The remaining outer surface of the 10 mold drum whichmaintained sliding contact with the distributing nozzle produced holesin the back of the product which in the case of artificial turf serve asdrain holes. After compacting and heat setting to form a product asshown in FIG. 9, the material was collected on a mandrel in the form ofa continuous strip of artificial turf.

Example 2 This example illustrates an artificial grass product that canbe made following the teaching of the prior art wherein no provision ismade to maintain differential pressures within the mold.

Apparatus was used identical to Example 1, except only one set ofpolymer ports was provided, the set feeding the tufts. No pressurefingers were provided. Mold shape and temperatures as well as coolingwater conditions were the same as Example 1. When polymer pressure was500 p.s.i. at the end of the extruder, and 250 p.s.i. at the dischargeend of the metering parts, a product was produced having tufts highabove the stringers, and no leakage occurred from the stringer groovesupstream of the polymer block. When polymer flow to the mold wasincreased, severe leakage occurred along the stringer groove to theupstream side of the polymer block, even though the extruder pressureremained below 550 p.s.i. The tufts thus produced were still only high.

Example 3 This example illustrates a method used to produce a continuousmolded structure suitable for use as an artificial ski slope.

Apparatus used is in accordance with FIGS. 1 and 15.

Polypropylene pellets are melted and fed under hydraulic pressure from ascrew extruder to a special distributing nozzle previously describedhaving two rows of polymer supply holes. The first row of holesdirecting polymer into the deep tapered cylindrical cavities and lateralgrooves in the mold drum. The second row directing polymer to recessesin the special nozzle from which polymer is extruded as stringers ontothe outer surface of the mold drum. Restrictors are employed to controlthe amount of polymer supplied to each stringer.

Typical conditions for this process are as follows: melt temperature atextruder exit, 500 F.; nozzle temperature, 400 F.; temperature of themold drum surface, F.; pressure at end of extruder barrel, 1500 p.s.i.;molding pressure (cavities), 1250 p.s.i., molding pressure (stringers),50 p.s.i.; total force holding drum in contact with nozzle, 10,000 lbs.;peripheral speed of drum, 4 f.p.m.; cooling time before stripping, 30seconds.

The final product takes the form of a series of cylindrical projectionsdiameter at root with a concave tapered outer surface reducing thisdiameter to ,4 over a length of 1%". These members spaced on A" centerswidthwise and lengthwise, are connected laterally by a filler piece wideby ,4 deep, and longitudinally by overlaid stringers V wide by V deep.

Example 4 This example illustrates a method one would use to produce acontinuous molded structure suitable for use as an artificial soilretention media on slopes or gradients.

Apparatus used and process conditions are in accordance with Example 1,except that tuft cavities would be replaced by a T section slot the fullwidth of the product as shown in FIG. 21. The cross section of the T onthe outer surface of the drum being 7 wide and 3%" deep and the leg ofthe T being A; thick at the root, tapering to A thick at an overalldepth of one inch. Spacing of stringers and Ts would be on approximately2" centers.

It would be apparent from the foregoing disclosure by those skilled inthe art that several modifications may be made to the apparatus forcarrying out the processes for 11 producing the variety of products astaught by this invention. Accordingly, there is no intention of limitingthe scope of the invention in any way except as those limitations setforth in the appended claim.

What is claimed is:

1. A three-dimensional integrally fused molded product comprising aplurality of parallel and spaced apart base strips arranged to form aplane, a plurality of spacedapart cups residing in parallel rows betweensaid parallel base strips and being integrally connected to two adjacentbase strips to form a connecting bridge therebetween, said cups definingan opening in the area between said strips for drainage, said cupshaving cup walls extending outwardly from a common strip plane surface,cup rims limiting the outward extension of said cup walls and aplurality of elongated cup projections being integral with 12 said cupwalls and extending outwardly from said cup rims.

References Cited UNITED STATES PATENTS 3,390,044 6/1968 Malakofi l61-623,312,583 4/1967 Rochlis 161-62 3,317,644 5/1967 Takai 16l62 3,235,4382/1966 Wisotzky 16 162 WILLIAM A. POWELL, Primary Examiner P. J.THIBODEAU, Assistant Examiner US. Cl. X.R.

